Flexible rotary shaft



July 15, 1952 H. NIELD FLEXIBLE ROTARY SHAFT Filed NOV. 19, 1946 2 SHEETS-SHEET 1 July 15, 1952 H. NIELLD FLEXIBLE ROTARY SHAFT 2 SHEETS-SHEET 2 15.11... I men-ma HERBERT NiELo BY a 6 3| z B1 6.1 II.

I on n Filed Nov. 19, 9.946

Patented July 15, 1952 UNITED STATES FLEXIBLE ROTARY SHAFT Herbert Nield, Caulfield, Victoria, Australia Application November 19, 1946, Serial No. 710,820 In Australia November 19, 1945 This invention relates to flexible drive shafts of the type which are adapted to transmit rotary motion whilst curved lengthwise.

Hitherto such types of flexible rotary shafts have consisted of a series of interfltting coiled springs which are adapted to twist and flex whilst transmitting the drive. Such devices were necessarily limited in use to the transmission of low torques.

The primary object of the present invention is to provide an improved flexible rotary shaft which is capable of effectively transmitting much higher torques than hitherto over a relatively wide range of speed and if necessary around curves of relatively small radii.

Another object is to provide an improved flexible rotary shaft which is of relatively simple and inexpensive design havingfew Working parts which are not liable to get out of order or require replacement. I

Other objects and novel constructional features of the invention will be more readily apparent from the following description.

Referring to the drawings which form part of this speciflcationi Fig. l is a part sectional elevation of a flexible rotary shaft in accordance with one embodiment of the present invention.

Fig. 2 is a transverse sectional elevation on an enlarged scale of a pair of the interfitting shaft sections seen in Fig. 1.

Fig. 3 is a sectional elevation showing a series of the shaft sections in operative engagement.

Fig. 4 is a face or end view of 2.

Figs. 5 and 6 are a'sectional elevation and an end view respectively of portion of a flexible rotary shaft in accordance with a modification.

Figs. 7 and 8 are a sectional elevation and an end view respectively of portion of a flexible rotary shaft in accordance with another embodiment of the invention.

Figs. 9 and 10are a sectional elevation and an end view respectively of portion of a flexible rotary shaft in accordance with a further embodiment of the invention.

Fig. 11 is a transverse sectional elevation of a shaft section similar to the type seen in Fig. 2 but which is composed of sheet metal stampings.

Figs. 12 and 13 are a transverse section and a side elevation respectively of a shaft section in accordance with a still further embodiment.

Figs. 14; 15, 16;,and 1'? are fragmentary sectional elevations on an. enlarged scale showing several types of outercasings for the flexible rotary shaft.

1 Claim. (Cl. 642) The improved flexible rotary shaft includes a pair of coupling members 2 and 3 respectively located one at each end of the shaft and which are adapted respectively for removable connection to a driving unit and a driven unit. For example, as seen in Fig. 1, one of the coupling members 2 may be of hollow tubular formation and fltted with a grub screw or the like 4 whereby it may be detachablyconne'cted to a driving shaft. Alternatively the coupling member may be screwed or connected in any other suitable manner to the driving shaft.

The coupling member 3 at the opposite end of the flexible shaft may also vary considerably in accordance with-requirements. Forinstance it may consist of a series of cylindrical sections 6 of progressively reduced diameter and arranged in axial alignment so as to be capable of fitting within sleeves, collars, bearings orthe like of various sizes.

Located between the pair of spacedcoupling members is a series of independent shaft sections. 1 each of which is preferably of; circular shape With the opposite side faces 8 of conical or annularly and radially flat formation. The central body portion of the shaft section forms a common baseand the cone apices arelocated in axial alignment but pointing in opposite directions. I

An open ended axial hole 9 is formed through each shaft section so as to extend through the opposed apices. A flexible tie element H, preferably in the form of a stranded wire cable or the like, passes through the holes in the series of shaft sections and is anchored at its opposite ends by clamping screws I2 or in any other suit- .able manner to the coupling members 2 and 3.

The series of shaft sections'are adapted to be operatively interengaged for transmitting rotary motion irrespective of whether the shaft is curved lengthwise and for this purpose a series of driving connections is provided on the opposite conical faces of each shaft section I. I All of said driving connections consist of a series of circumferentially spaced inwardly tapered radial teeth [3 on the opposite-conical faces of each shaft section. Each tooth may be of substantially triangular formation in plan with its axis extending ing -'in opposite directions.

radially or substantially radially to the axis of its shaft section.

The series of teeth on each side of the shaft section are spaced apart by pockets M which are of complementary formation, the teeth on each conical face preferably being staggered in relation to the teeth of the opposite face so that each tooth is aligned with a pocket on the opposite conical face of itsshaft section.

The width of the aforesaid pockets may be such that the opposite side walls of each pocket are adapted to form part of the opposed side faces of adjacent teeth without any intervening ledges-or shoulders. The height of the teeth above the adjacent conical surface may be-=substantially the same as the depth of said pockets sotha-ttheef fective side faces of each tooth are:substantiall-y symmetrical about the conical surface. 7

As seen more clearly in Fig. 2 the outer-or end face I6 of each tooth may be substantially parallel to that portion of the conical-surface 81which is diametrically 1 opposite onthe same. side of its shaft section.

In order to provide efficient rolling contact 'between the adjacent shaft sections'when inuse,

each shaft section is preferablyof circular-or substantially circular :formation .and the length of the teeth f3 may be-such thatxthey terminate conical surface on the central apex portionof the shaft sectionat the same side thereof.

In use, shaftsections I of the type .illustrated in Figs. 2, 3 and i of the-drawings. are assembled upon the flexible tie element :II which is .an-

chored to the end coupling'members 2 and -3 in such a manner that the intervening shaft sections aredrawninto engagement witheach other with-the series'ofteeth Son-each section fitting within the co-aligned pockets l4 on the opposed face of the adjacent shaft section. As all of the conical faces of the interengaged shaft sections are in rolling engagementit follows that'the shaft may be curved lengthwise within the limit imposed by the taper of said conical faces without interfering with therotation'of the shaft. The heightiof the teeth and the depth of thepockets is predetermined in relation to thetaper-o'flthe conical faces with 'the result that "the teeth and pockets at Fboth the inside and .the outside :of the neutralaxis .of the shaft remain inengagement irrespective of the curvature of :the rotating shaft. Itawillibe readily apparent that this arrangement enables relatively a'high -torque to be transmitted, if necessary, at a relatively high speed as-may berequired. Y

If desired insteado'f being staggered as aforesaid, the series -of teeth -'-and pockets at opposite sides of eachsha'ft section 1 may be co-aligned so that each pair 1 of opposed pockets merge into an'openended slot.

According to a modification as illustrated in Figs.-5 and 6, -each of-the-shaft sections! is;provided with oppositeside faces- 8- of conical orannularly and radially flat formation as aforesaid with the coneapices in axial alignment but'point- In this case-an enlarged open ended *central aperture l 1 is formed axially through the shaftsection and;a series of circumferentially ;spaced radial ,pockets 1'4 are formed in "each 'of the conical faces with the 4 pockets separated by a series of dividing webs or teeth I'8 extending substantially radially of the shaft section.

In this case the driving connections include a series of separate key members I 9 each of which includes a hub portion 2| adapted to fit within the aforesaid central aperture l1 and which is provided with an open ended axial hole 9 through the hub portionito passthdfiexibletie element I I.

Each hub portion carries-a seriesof'radial arms or teeth 22 which may be formed integral therewith and be adapted to fit within pairs of co- :aligned pockets M in the opposed faces of adjacent shaft sections 1 when the latter are assembled on the tie-element. As seen more clearly .in.-Eig..5 this=arrangement also enables the drivting sections between the shaft sections to remain interengaged at both the inside and out- =side-of the neutral axis of the shaft irrespective of the curvature thereof within the limits imposed by.the:taper.;of1the opposed conical 'faces.

'Another embodiment Jis illustrated in Figs. 7 and 8 of the drawings. .In.this.case the driving connections IfOl :operatively interengaging the shaft sections :1 include ;a. series of circumferentially spaced'pockets formed in the opposite conical faces 3810f each shaft section, the pockets being separated by:a series of substantially radial webs I8. These pockets are adapted to accommodatea series-of independent key elements 24 each of whichis.adapted-to-fitwithin a pair of co-aligned .pocketsinzthe opposed faces of-adjacentsshaftisections when the latter are assembled on the flexible Ltie element.

In order to prevent lthe;independent key elements 24 being displacedduring'rotation by centrifugalaction,'suitablekey retaining means are employed. 'For example, :said retaining means may consist of a plurality of separated rings2B which may be of substantially T or L shape in cross section;so as to provide flanges 21 which overhang theiouter ends of the key elements and retain them in :the desired operative position. Alternatively'the'retaining'flanges may be formed integral with the shaft sections'if so desired.

1Eigs..9 and '10 illustrate;a;still,further embodi- .ment in which the driving :connections between the series of conical shaft :sections 1 comprise a series of circumferentiallyzspacedholes 28 formed in the opposite .conical faces :of each shaft section. The arrangementissuch .that when the shaft sections are assembleditheholes in the opposed faces of adjacent shaft sections are coaligned so asto=slidably;accommodate the opposite end portions .of a iseriesof connecting pins 29. The relativesizes of the .holesand pins is such as to permit free .endwise sliding movement of the pins within the .holes during the rolling engagement 'of the :shaft .sections whilst the shaft is rotating.

The depth of the holes 28 may be such that they do not extend completely through their shaft section but-are closed at the'inner end to form a"blin'd hole. As seen more clearly in Fig. 10, the holes in the oppositeconical faces of each shaft section are preferably arranged out of alignment so that adjacent holes on the same side are separated by a blind hole extending inwardlyfrom the-opposite 'side of the shaft section.

According to a modification of the last mentioned embodiment a series of open ended holes are employed instead of blind holes as aforesaid. In this casethe spacing between the holes is varied so that when the shaft sections are assembled upon the flexible tie element the connecting pins 29 are prevented from sliding lengthwise between more than two of the shaft sections. j V

Shaft sections of the type illustrated in Figs. 2, 3 and 4 are preferably formed by casting, forging or in any other suitable manner. It will be appreciated, however, that ithefshaft sections may be formed from sheet metal if'so desired. Fig. 11 illustrates one such embodiment wherein the shaft section is of hollow formation and consists of a pair of metal stampings 3| which are secured at their abutting marginal portions as at 32 by welding or in any other suitable manner. The stampings may be stiffened and spaced apart by a central spacing member 33 having an open ended axial hole 34 formed therethrough to pass the flexible tie element H. Each of the metal stampings is' provided with a series of circumferentially spaced teeth 13 and intervening pockets [4 as aforesaid.

Figs. 12 and 13 illustrate another type of sheet metal construction in which the shaft sections 1 are also of hollow formation and consist of a pair of metal stampings 3! which are corrugated radially as at 36 so as to form a series of teeth on the opposite conical faces. The corrugated stampings are adapted to be interengaged and secured together at their marginal edges in any suitable manner. This construction also preferably includes a central spacing member 33 having an open ended axial hole 34 therethrough to pass the flexible tie element.

In order to exclude dust, grit and other foreign matter from the interengaged shaft sections and also to maintain effective lubrication thereof, the assembled shaft section 1 are preferably provided with an outer casing of a flexible character which is adapted for connection at its opposite ends to the coupling members 2 and 3. The type of outer casing employed may vary widely, several suitable types being illustrated by way of example in Figs. 14 to 1'7 of the drawings.

As seen in Fig. 14 the casing may consist of a series of ring like collars 38, one or both edges of which is or are turned down so as to form a circumferential lip or lips 39. Each of these lips is adapted to be retained within a circumferential recess 4| formed in the outer edge portion of each shaft section in such a manner that the body portion of the collar is adapted to bridge the gap between adjacent shaft sections when the latter are assembled on the flexible tie element.

Alternatively the ring like collars 38 may be straight sided and be retained between circumferential ribs 42 on the outer edge portion of each shaft section as seen in Fig. 15. These ribs may be formed integral with the shaft sections 01' they may consist of separate rings accommodated in grooves in the outer edges of the shaft sections.

Another embodiment is illustrated in Fig. 16 in which each of the ring like collars 38 is provided with an inwardly projecting circumferential rib 43 located approximately midway in the width of the collar. Endwise movement of the collar is restrained by the rib being engaged by the shoulders of complementary circumferential recesses 44 formed in the opposed edge portions of adjacent shaft sections.

A still further type of outer casing is illustrated in Fig. 17. In this embodiment the casing consists of an open ended tubular sheath 46 which may be composed of rubber or any other suitable resilient material. The sheath is preferably provided with a series of longitudinally spaced and inwardlyprojecting ribs 41 which extend circumferentially of the shaft and are adapted tofit within circumferential grooves 48 in the outer edge portions of the shaft sections.

The inner end portions of the aforesaid couplings 2 and 3 are provided with conical faces and driving connections 49 suitable for engaging the adjacent shaft sections on the flexible tie element. In addition any suitable type of intermediate guide bearing or the like may be provided for supporting the flexible drive shaft at one or more points in the length thereof in order to prevent the possibility of "whip developing at certain speeds. v

For example the aforesaid outer casing may consist of a known type of flexible metallic conduit of helically wound formation. This casing is preferably fitted with an anti-friction lining which may consist of a helically wound tape of bronze or any other suitable material. In order to prevent binding, the outer casing and its lining are preferably Wound in opposite directions.

Such a lined outer casing enables the shaft, when curved, to be adequately supported simply by connecting the casing at one or more immediate points in its length to a clamp, bracket or any other suitable fixture whereby the lining serves as a bearing and prevents whip or other undesirable bodily movement from developing.

If desired the flexible tie element Il may be spring influenced at one or both ends thereof in order to provide a yielding engagement between the various driving connections on the series of shaft sections.

It will be appreciated from the foregoing that the improved flexible rotary shaft possesses many advantages over the coiled spring type of drive shaft and that it may be readily adapted for a wide variety of purposes. In this regard the improved shaft sections are not limited in use to a flexible rotary shaft of the kind indicated but may be readily adapted to function as a universal joint if so desired. For this purpose the inner ends only of a pair of elongated shaft sections are provided with conical faces and a series of driving connections which are retained in interengagement by a flexible tie element as aforesaid.

It is also to be understood that various other alterations, modifications, and/or additions may be introduced into the construction and arrangement of parts above described without departing from the ambit of the invention as defined by the appended claim.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

An improved flexible rotary shaft comprising a series of abutting independent shaft sections each of which has opposite side faces of conical formation and the cone apices in axial alignment but pointing in opposite directions, each shaft section having an open ended axial hole passing through said apices, a flexible tie element passing through said holes in the series of shaft sections and which is anchored at its opposite ends to a pair of coupling members so as to maintain the abutting portions of adjacent shaft sections in engagament, a series of driving connections on each of the opposite conical faces of each shaft section and on said coupling members for operatively interengaging said shaft sections in such a manner that when the drive shaft is curved lengthwise, all ofsaid. driving .connections on. ad-

.joiningjhaltt sections .remaini ininterenga'gement both .at ltheiinsi'cie .andthe outside 'of the neutral taperof said conical faces, sai'd driving connections comprising iinterengaged substantially triangular shaped 'teethrintermediate radially inner and router portions of earth shaft section and substantially triangular shaped closed pockets between said inner and outer portions and between the teeth.

HERBERT NIELD.

REFERENCES CITED The following references are ofirecorcl in the file of this patent:

UNITED STATES PATENTS Number Number Name Date lBeekman- Mayf23, 1893 Weedeler Mar. 26, 1901 Granville Dec. 17, 1929 FOREIGN PATENTS Country Date GreatiBritain 1890 GreatBritain .1889 

